KR20230022108A - Water-dispersed pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet - Google Patents

Abstract

The present invention provides a water-dispersible adhesive composition suitable for securing adhesion while maintaining low viscosity during filtering and appropriate viscosity recovery during a coating process, and an adhesive sheet comprising an adhesive layer formed from the composition. The water-dispersible adhesive composition of the present invention contains a water-dispersible polymer, a carboxylic acid-based copolymer thickener, a polyacrylic acid thickener, and water. The proportion of the carboxylic acid-based copolymer thickener in the solid content of the water-dispersible adhesive composition is 0.1 mass% or more and 1.5 mass% or less. The proportion of the polyacrylic acid thickener in the solid content is 1 mass% or more and 3.7 mass% or less. The adhesive sheet (X) of the present invention includes an adhesive layer (10) formed of such a water-dispersible adhesive composition.

Description

Water dispersion type adhesive composition and adhesive sheet {WATER-DISPERSED PRESSURE-SENSITIVE ADHESIVE COMPOSITION AND PRESSURE-SENSITIVE ADHESIVE SHEET}

The present invention relates to a water-dispersible pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet.

The display panel has a laminated structure including elements such as, for example, a pixel panel, a polarizing film, a touch panel, and a cover film. In the manufacturing process of such a display panel, for example, an optically transparent adhesive sheet is used for bonding elements included in the laminated structure. And, for the PSA sheet for display panel use of personal devices such as mobile devices and wearable devices, in addition to the purpose of environmental measures, in order to avoid the influence of organic solvents on the human body, the PSA sheet formed of the water-dispersible PSA composition development is in progress. The technology related to the water-dispersible pressure-sensitive adhesive composition is described, for example, in Patent Document 1 below.

Japanese Unexamined Patent Publication No. 2021-134274

The above-mentioned adhesive sheet is manufactured, for example, as follows. First, a water dispersion type adhesive composition is prepared by mixing water as a solvent, a water dispersion type base polymer, and various components (water dispersion type tackifying resin, leveling agent, antifoaming agent, thickener, etc.) to be blended as necessary. Next, the water-dispersible pressure-sensitive adhesive composition is filtered through a filter (filtering step). Next, on the plastic substrate, the water dispersion type pressure-sensitive adhesive composition is applied with a coater to form a coating film (coating step). Next, the coating film on the plastic substrate is dried to form an adhesive layer.

A high degree of cleanliness is required for adhesive sheets for use in display panels. For this reason, in the filtering step described above, a filter having a small pore diameter is used for removing minute foreign matters from the water-dispersible pressure-sensitive adhesive composition. From the viewpoint of filter liquid permeability during such filtering, the lower the viscosity of the water-dispersible pressure-sensitive adhesive composition, the better.

On the other hand, in the coating process described above, the water-dispersible pressure-sensitive adhesive composition is applied onto the plastic substrate by a coater. During coating, a relatively large shear force acts on the water-dispersible pressure-sensitive adhesive composition, and the viscosity of the composition temporarily decreases. After being applied on the plastic substrate, the water-dispersible pressure-sensitive adhesive composition is released from the shear force and its viscosity is restored. However, when the viscosity of the water-dispersible pressure-sensitive adhesive composition immediately after viscosity recovery is excessively low, the water-dispersible pressure-sensitive adhesive composition aggregates on the plastic substrate (occurrence of agglomeration). In the coating process, from the viewpoint of suppression of clumping, the higher the viscosity immediately after the viscosity recovery of the water-dispersible pressure-sensitive adhesive composition is good. In addition, when the viscosity of the water-dispersible pressure-sensitive adhesive composition immediately after recovery is excessively high, coating traces remain in the form of streaks on the coated water-dispersible pressure-sensitive adhesive composition. From the viewpoint of suppression of coating traces, it is preferable that the viscosity of the water-dispersible pressure-sensitive adhesive composition immediately after viscosity recovery is not excessively high.

In addition, adhesive strength for securing the bonding reliability between adherends is also required for the adhesive sheet formed from the water-dispersible pressure-sensitive adhesive composition.

The present invention provides a water-dispersible pressure-sensitive adhesive composition suitable for ensuring adhesive strength while achieving both low viscosity during filtering and appropriate viscosity recovery during the coating process, and a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the composition.

The present invention [1] is a water-dispersible pressure-sensitive adhesive composition containing a water-dispersible polymer, a carboxylic acid-based copolymer thickener, a polyacrylic acid thickener, and water, wherein the ratio of the carboxylic acid-based copolymer thickener to the solid content of the water-dispersible pressure-sensitive adhesive composition is 0.1 It is mass % or more and 1.5 mass % or less, and the ratio of the said polyacrylic acid thickener in the said solid content is 1 mass % or more and 3.7 mass % or less, It contains the water dispersion type adhesive composition.

The present invention [2] includes the water-dispersible pressure-sensitive adhesive composition according to [1] above, wherein the total ratio of the carboxylic acid-based copolymer thickener and the polyacrylic acid thickener in the solid content is 2% by mass or more and 4.2% by mass or less.

This invention [3] contains the water-dispersible adhesive composition as described in said [1] or [2] whose viscosity on the shear rate 4s ^-1 and 30 degreeC conditions is 0.8 Pa.s or less.

In the present invention [4], after shearing at a shear rate of 1×10 ⁴ s ^-1 and 30°C, the viscosity under the conditions of a shear rate of 4 s ^-1 and 30°C is 0.9 Pa·s or more and 1.5 Pa·s or less. , The water dispersion type pressure-sensitive adhesive composition described in any one of the above [1] to [3] is included.

The present invention [5] includes the water-dispersible pressure-sensitive adhesive composition according to any one of [1] to [4], wherein the water-dispersible pressure-sensitive adhesive composition further contains a tackifier.

The present invention [6] includes the water-dispersible pressure-sensitive adhesive composition according to any one of [1] to [5], wherein the water-dispersible pressure-sensitive adhesive composition further contains a leveling agent.

This invention [7] contains the adhesive sheet containing the adhesive layer formed from the adhesive composition in any one of said [1]-[6].

The present invention [8] includes the pressure-sensitive adhesive sheet according to [7], wherein the pressure-sensitive adhesive layer has a thickness of 40 µm or less.

As described above, the water-dispersible pressure-sensitive adhesive composition of the present invention contains, in addition to the water-dispersible polymer and water, 0.1 to 1.5% by mass (ratio in solid content) of a carboxylic acid-based copolymer thickener and 1 to 3.7% by mass of a polyacrylic acid-based thickener. do. Such a water-dispersible pressure-sensitive adhesive composition is suitable for ensuring adhesive force while achieving both low viscosity during filtering and moderate viscosity recovery during the coating process.

1 is a schematic cross-sectional view of an embodiment of the pressure-sensitive adhesive sheet of the present invention.

A water-dispersible pressure-sensitive adhesive composition according to an embodiment of the present invention is an aqueous emulsion containing a water-dispersible polymer, a carboxylic acid copolymer thickener, a polyacrylic acid thickener, and water.

Examples of the water dispersion type polymer include water dispersion type acrylic polymers, water dispersion type urethane polymers, water dispersion type polyaniline polymers, and water dispersion type polyester polymers. Preferably, water dispersion type acrylic polymers are used. do. The said acrylic polymer is a polymer of the monomer component containing an alkyl (meth)acrylic acid ester in a ratio of 50 mass % or more. '(meth)acryl' means acryl and/or methacryl.

As an alkyl (meth)acrylate, the (meth)acrylic acid alkylester which has a linear or branched C1-C20 alkyl group is mentioned, for example. Examples of such alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isopropyl (meth)acrylate, and iso(meth)acrylate. Butyl, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, (meth)acrylate ) undecyl acrylate, (meth) dodecyl acrylate, (meth) acrylate isotridodecyl, (meth) acrylate tetradecyl, (meth) acrylate isotetradecyl, (meth) acrylate pentadecyl, (meth) acrylate hexadecyl, Heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. (meth)acrylic-acid alkyl ester may be used independently, and 2 or more types may be used together. As the (meth)acrylic acid alkyl ester, preferably, an acrylic acid alkyl ester having an alkyl group of 1 to 12 carbon atoms is used, more preferably, an acrylic acid alkyl ester having methyl acrylate and an alkyl group of 2 to 8 carbon atoms is used, and still more preferably Preferably, methyl acrylate and 2-ethylhexyl acrylate are used.

The ratio of the (meth)acrylic acid alkyl ester in the monomer component is preferably 70 mass% or more, more preferably 80 mass%, from the viewpoint of appropriately expressing basic properties such as adhesiveness in the adhesive layer formed from the water-dispersible pressure-sensitive adhesive composition. % or more, more preferably 90 mass% or more, particularly preferably 95 mass% or more, and preferably 99.5 mass% or less, more preferably 99 mass% or less.

The monomer component may contain a copolymerizable monomer copolymerizable with (meth)acrylic acid alkyl ester. As a copolymerizable monomer, a polar group containing monomer is mentioned, for example. Examples of the polar group-containing monomer include a carboxy group-containing monomer, a hydroxyl group-containing monomer, a nitrogen atom-containing ring-containing monomer, a silanol group-containing monomer, a sulfo group-containing monomer, a cyano group-containing monomer, and a glycidyl group-containing monomer. The polar group-containing monomer is useful for modifying the acrylic polymer, such as securing the cohesive force of the acrylic polymer. A copolymerizable monomer may be used independently and two or more types may be used together.

Examples of the carboxy group-containing monomer include acrylic acid, methacrylic acid, 2-carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. The monomer component preferably contains a carboxy group-containing monomer, more preferably acrylic acid or methacrylic acid, and particularly preferably acrylic acid, from the viewpoint of ensuring the adhesiveness of the pressure-sensitive adhesive layer formed of the water-dispersible pressure-sensitive adhesive composition. and methacrylic acid are used in combination.

The ratio of the carboxy group-containing monomer in the monomer component is preferably 0.5% by mass or more, more preferably 1% by mass or more, still more preferably from the viewpoint of securing the cohesive force of the pressure-sensitive adhesive layer formed from the water-dispersible pressure-sensitive adhesive composition. It is 1.5 mass % or more. The ratio of the carboxyl group-containing monomer in the monomer component is preferably 8% by mass or less, more preferably 5% by mass or less, still more preferably 3% by mass, from the viewpoint of avoiding the risk of corrosion of the adherend by acid. below

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and (meth)acrylate. 4-hydroxybutyl acrylate, (meth)acrylate 6-hydroxyhexyl, (meth)acrylate 8-hydroxyoctyl, (meth)acrylate 10-hydroxydecyl, (meth)acrylate 12-hydroxylauryl, and (meth)acrylate and 4-hydroxymethylcyclohexyl)methyl (meth)acrylate.

Examples of the monomer having a nitrogen atom-containing ring include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, and N-vinylpiperazine. , N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one , N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, N-vinylisothiazole, and acryloylmorpholine.

Examples of the silanol group-containing monomer include 3-methacryloxypropyltrimethoxysilane and 3-acryloxypropyltrimethoxysilane.

Examples of the sulfo group-containing monomer include styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidepropanesulfonic acid, and sulfopropyl(meth)acrylic acid. rate, and (meth)acryloyloxynaphthalenesulfonic acid.

As a phosphoric acid group containing monomer, 2-hydroxyethyl acryloyl phosphate is mentioned, for example.

Examples of the cyano group-containing monomer include acrylonitrile and methacrylonitrile.

Examples of the glycidyl group-containing monomer include glycidyl (meth)acrylate and 2-ethylglycidyl ether (meth)acrylate.

The water dispersion type acrylic polymer can be formed, for example, by emulsion polymerization of the above monomer components. In emulsion polymerization, for example, first, a monomer emulsion is prepared by stirring a mixture containing a monomer component, an emulsifier, and water. Next, a polymerization initiator is added to the monomer emulsion to initiate a polymerization reaction. In this polymerization reaction, a chain transfer agent may be used to adjust the molecular weight of the acrylic polymer. As the polymerization method, drop polymerization or batch polymerization may be used. The polymerization time is, for example, 0.5 to 10 hours. The polymerization temperature is, for example, 50°C to 80°C.

Examples of the emulsifier include anionic emulsifiers, nonionic emulsifiers, and radically polymerizable emulsifiers (reactive emulsifiers).

Examples of the anionic emulsifier include sodium polyoxyethylene lauryl sulfate, sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkyl ether sulfate, polyoxyethylene alkylphenyl ether ammonium sulfate, and polyoxyethylene. sodium alkyl phenyl ether sulfate, and sodium polyoxyethylene alkyl sulfosuccinate.

Examples of the nonionic emulsifier include polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, and polyoxyethylene polyoxypropylene block polymer.

Examples of the radically polymerizable emulsifier (reactive emulsifier) include an emulsifier in which a radically polymerizable functional group is introduced into the anionic emulsifier or the nonionic emulsifier. As this radically polymerizable functional group, a vinyl group, a propenyl group, an isopropenyl group, a vinyl ether group, and an allyl ether group are mentioned, for example. As the reactive emulsifier, specifically, ammonium-α-sulfonate-ω-1-(allyloxymethyl)alkyloxypolyoxyethylene is preferred. When a reactive emulsifier is used as the emulsifier, the water-dispersible acrylic polymer obtained by emulsion polymerization contains a monomer unit derived from the reactive emulsifier. That is, the emulsifier is blown into the acrylic polymer. For this reason, when the adhesive layer formed from the water-dispersible pressure-sensitive adhesive composition is adhered to an adherend, contamination of the adherend with the emulsifier (low molecular weight component) can be suppressed.

An emulsifier may be used independently or two or more types may be used together. The blending amount of the emulsifier is, for example, 0.5 parts by mass or more, and, for example, 5 parts by mass or less with respect to 100 parts by mass of the monomer component.

As a polymerization initiator, an azo polymerization initiator and a peroxide polymerization initiator are mentioned, for example. Examples of the azo polymerization initiator include 2,2'-azobis{2-[N-(2-carboxyethyl)amidino]propane}, 2,2'-azobisisobutyronitrile, and 2,2'-azo Bis(2-amidinopropane)dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, and 2,2'- and azobis(N,N'-dimethyleneisobutylamidine). As a peroxide polymerization initiator, benzoyl peroxide, t-butyl hydroperoxide, and hydrogen peroxide are mentioned, for example. A polymerization initiator may be used independently, and 2 or more types may be used together. The compounding amount of the polymerization initiator is, for example, 0.01 parts by mass or more, and, for example, 2 parts by mass or less, based on 100 parts by mass of the monomer component.

Examples of the chain transfer agent include glycidylmercaptan, mercaptoacetic acid, 2-mercaptoethanol, t-laurylmercaptan, t-dodecanethiol, thioglycolic acid, 2-ethylhexyl thioglycolic acid, and 2, and 3-dimercapto-1-propanol. A chain transfer agent may be used independently and two or more types may be used together. The compounding amount of the chain transfer agent is, for example, 0.001 part by mass or more and 0.5 part by mass or less with respect to 100 parts by mass of the monomer component.

By such emulsion polymerization, the water-dispersible acrylic polymer is prepared as a polymer emulsion (aqueous dispersion in which the water-dispersible acrylic polymer is dispersed in water).

The weight average molecular weight (Mw) of the water-dispersible acrylic polymer is, for example, 100000 or more, preferably 300000 or more, and, for example, 5000000 or less, preferably 3000000 or less. The weight average molecular weight of the acrylic polymer is measured by gel permeation chromatography (GPC) and calculated in terms of polystyrene.

The water dispersion type polymer has a glass transition temperature (Tg) of, for example, 20°C or lower, preferably 0°C or lower.

The carboxylic acid-based copolymer thickener is an emulsion-type thickener composed of a carboxylic acid-based copolymer. The carboxylic acid-based copolymer is, for example, a copolymer of monomer components containing a carboxy group-containing acrylic monomer. Examples of commercially available carboxylic acid copolymer thickeners include "Aaron B-300K", "Aaron B-500", "Aaron A-7055" and "Aaron A-7075" manufactured by Toagosei Co., Ltd., preferably. 'Aaron B-500' is used. The viscosity of a 1% dilution of a commercial product (aqueous solution product) of a carboxylic acid copolymer thickener measured by a BM type viscometer at 25°C, pH 8 to 9 and conditions of 60 rpm is preferably 10000 mPa s or less, more preferably It is 1200 mPa·s or less, and is preferably 10 mPa·s or more, more preferably 1000 mPa·s or more. A carboxylic acid-type copolymer thickener may be used independently or two or more types may be used together.

The ratio of the carboxylic acid-based copolymer thickener in the solid content of the water-dispersible pressure-sensitive adhesive composition is 0.1% by mass or more, preferably 0.3% by mass or more, from the viewpoint of securing thickening by the carboxylic acid-based copolymer thickener in the water-dispersible pressure-sensitive adhesive composition. More preferably, it is 0.4 mass % or more, More preferably, it is 0.5 mass % or more. The ratio of the carboxylic acid-based copolymer thickener in the solid content of the water-dispersible pressure-sensitive adhesive composition is 1.5% by mass or less, preferably 1.3% by mass or less, from the viewpoint of avoiding excessive thickening by the carboxylic acid-based copolymer thickener in the water-dispersible pressure-sensitive adhesive composition. More preferably, it is 1.1 mass % or less, More preferably, it is 0.9 mass % or less. The solid content of the water-dispersible pressure-sensitive adhesive composition is a component other than water in the water-dispersible pressure-sensitive adhesive composition, specifically, water-dispersible polymer, carboxylic acid-based copolymer thickener, polyacrylic acid thickener, and other components (leveling agent and adhesive) blended as necessary. grants, etc.).

Examples of the polyacrylic acid thickener include polyacrylic acid (a homopolymer of acrylic acid), sodium polyacrylate, and ammonium polyacrylate. Examples of commercially available polyacrylic acid thickeners include "Aron A-10H" (polyacrylic acid), "Aron A-20L" (sodium polyacrylate), "Aron A-7100" (sodium polyacrylate), and Aaron A-30' (ammonium polyacrylate), and 'Aaron A-7195' (ammonium polyacrylate), and 'Aaron A-10H' is preferably used. The viscosity at 25°C of a commercial product (aqueous solution product) of the polyacrylic acid thickener is preferably 50000 mPa·s or less, more preferably 40000 mPa·s or less, and more preferably 1000 mPa·s or more, preferably 5000 mPa·s. More than that. A polyacrylic acid thickener may be used independently or two or more types may be used together. The molecular weight of the polyacrylic acid thickener exhibiting such a viscosity is preferably 1,000,000 or less, more preferably 600,000 or less, and is preferably 50,000 or more, more preferably 100,000 or more.

The ratio of the polyacrylic acid thickener in the solid content of the water-dispersible pressure-sensitive adhesive composition is 1% by mass or more, preferably 1.4% by mass or more, more preferably from the viewpoint of securing the thickening by the polyacrylic acid thickener in the water-dispersible pressure-sensitive adhesive composition. It is 1.8 mass % or more, More preferably, it is 2 mass % or more. The proportion of the polyacrylic acid thickener in the solid content of the water-dispersible pressure-sensitive adhesive composition is 3.7% by mass or less, preferably 3% by mass or less, more preferably from the viewpoint of avoiding excessive thickening by the polyacrylic acid thickener in the water-dispersible pressure-sensitive adhesive composition. It is 2.8 mass % or less, More preferably, it is 2.6 mass % or less.

The total ratio of the carboxylic acid-based copolymer thickener and the polyacrylic acid thickener in the solid content of the water-dispersible pressure-sensitive adhesive composition is preferably 2% by mass or more, from the viewpoint of the balance between the first viscosity η ₁ and the second viscosity η ₂ described later. It is preferably 2.5% by mass or more, more preferably 2.7% by mass or more, and is preferably 4.2% by mass or less, more preferably 3.5% by mass or less, and still more preferably 2.9% by mass or less.

The water-dispersible pressure-sensitive adhesive composition may contain other components. Examples of other components include a leveling agent, a tackifier, a silane coupling agent, an antiseptic agent, a surfactant, a crosslinking agent, and an antistatic agent.

As a leveling agent, for example, "Neocol SW-C" (sodium dialkylsulfosuccinate, manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), "Neocol P" (sodium dialkylsulfosuccinate, manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), "Surphynol 420" ' (acetylene glycol ethylene oxide surfactant, manufactured by Nissin Chemical Industry Co., Ltd.), and 'Perex OT-P' (sodium dialkyl sulfosuccinate, manufactured by Kao Corp.). In addition, as a leveling agent, 'Nopcowet 50' (sulfonic acid-based anionic surfactant), 'SN wet 126' (modified silicone/special polyether-based surfactant), 'SN wet FST2' (polyoxyalkyleneamine) nonionic wetting agent), "SN Wet S" (nonionic wetting agent of polyoxyalkylene amine ether), and "SN Wet 125" (modified silicone surfactant) (all manufactured by San Novco Co., Ltd.). A leveling agent may be used independently and two or more types may be used together. From the viewpoint of ensuring good leveling properties in the water-dispersible pressure-sensitive adhesive composition, the leveling agent is preferably at least one selected from 'Neocol SW-C', 'Neocol P' and 'Perex OT-P'.

The blending amount of the leveling agent is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, still more preferably 0.8 part by mass, with respect to 100 parts by mass of the water-dispersible polymer, from the viewpoint of suppressing clumping of the water-dispersible pressure-sensitive adhesive composition. More than that. The blending amount of the leveling agent is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, still more preferably 1 part by mass or less, from the viewpoint of ensuring the adhesive properties of the water-dispersible pressure-sensitive adhesive composition.

Examples of the tackifier include tackifier resins such as rosin-based resins, rosin derivative resins, petroleum-based resins, terpene-based resins, phenol-based resins, and ketone-based resins. The blending amount of the tackifier is preferably 5 parts by mass or more, more preferably 5 parts by mass or more, with respect to 100 parts by mass of the water-dispersible polymer, from the viewpoint of the balance between the viscosity of the water-dispersible pressure-sensitive adhesive composition and the adhesiveness of the pressure-sensitive adhesive layer formed from the composition. Preferably 15 parts by mass or more, more preferably 20 parts by mass or more, particularly preferably 25 parts by mass or more, and preferably 50 parts by mass or less, more preferably 45 parts by mass or less, still more preferably 40 parts by mass is less than

Examples of the silane coupling agent include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxy. Silane is mentioned, Preferably 3-methacryloxypropyltrimethoxysilane is used. The blending amount of the silane coupling agent is, for example, 0.005 parts by mass or more, and, for example, 1 part by mass or less, with respect to 100 parts by mass of the water-dispersible polymer.

The water-dispersible pressure-sensitive adhesive composition does not contain an organic solvent. Such a water-dispersible pressure-sensitive adhesive composition is preferable from the viewpoint of reducing the environmental load.

The water-dispersible pressure-sensitive adhesive composition can be prepared, for example, by adding various components to an emulsion polymerization solution of a water-dispersible polymer. In addition, the water content of the water-dispersible pressure-sensitive adhesive composition is increased or decreased to adjust the solid content concentration.

The solid content concentration _of the water-dispersible pressure-sensitive adhesive composition is preferably 10% by mass or more, _more preferably 15% by mass or more, still more preferably 20 % by mass or more, particularly preferably 25% by mass or more, more preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 35% by mass or less, still more preferably 30% by mass or less, Especially preferably, it is 27 mass % or less.

The viscosity (first viscosity η ₁ ) under conditions of a shear rate of 4 s ⁻¹ and 30° C. in the water-dispersible pressure-sensitive adhesive composition is preferably 0.8 Pa·s or less from the viewpoint of ensuring filter passability in the later filtering step. , more preferably 0.7 Pa·s or less, still more preferably 0.6 Pa·s or less. The first viscosity η ₁ is preferably 0.1 Pa·s or more, more preferably 0.3 Pa·s or more, still more preferably 0.5 Pa·s or more, from the viewpoint of suppressing clumping when applied on a substrate after passing through a filter. am. The method for measuring the first viscosity η ₁ is as described later in the Examples.

In the water-dispersible pressure-sensitive adhesive composition, the viscosity (second viscosity η ₂ ) after shearing at a shear rate of 1×10 ⁴ s ⁻¹ and 30° C. and at a shear rate of 4 s ⁻¹ and 30° C. is From the viewpoint of suppression of agglomeration and streaks in the coating process, it is preferably 0.9 Pa·s or more, more preferably 1.0 Pa·s or more. The second viscosity η ₂ is preferably 1.5 Pa·s or less, more preferably 1.3 Pa·s or less, still more preferably 1.2 Pa·s or less, from the viewpoint of suppressing streak marks in the coating step. The method for measuring the second viscosity η ₂ is as described later with respect to Examples.

From the viewpoint of a balance between ensuring filter passability in the filtering step and suppression of clumps and streaks in the coating step, the ratio of the second viscosity η ₂ to the first viscosity η ₁ (η ₂ /η ₁ ) is preferably It is preferably 1.6 or more, more preferably 1.7 or more, more preferably 3 or less, more preferably 2.5 or less, still more preferably less than 2, and particularly preferably 1.9 or less.

As described above, the water-dispersible pressure-sensitive adhesive composition contains, in addition to the water-dispersible polymer and water, 0.1 to 1.5% by mass (ratio in solid content) of a carboxylic acid-based copolymer thickener and 1 to 3.7% by mass of a polyacrylic acid-based thickener. Such a water-dispersible pressure-sensitive adhesive composition is suitable for ensuring adhesive force while achieving both low viscosity during filtering and moderate viscosity recovery during the coating process. Specifically, it is as showing with a later Example and Comparative Example.

1 is a schematic cross-sectional view of an adhesive sheet (X) as an embodiment of the present invention. The pressure-sensitive adhesive sheet (X) includes a pressure-sensitive adhesive layer (10). The pressure-sensitive adhesive layer 10 has a sheet shape having a predetermined thickness. The pressure-sensitive adhesive layer 10 spreads in a direction (surface direction) orthogonal to the thickness direction. The adhesive layer 10 includes an adhesive face 11 and an adhesive face 12 opposite to the adhesive face 11 . 1 shows the state in which peeling liners L1 and L2 are bonded to the adhesive surfaces 11 and 12 of the adhesive layer 10 by way of example. The release liner L1 is disposed on the adhesive face 11 . The release liner L2 is disposed on the adhesive face 12 . In addition, the adhesive sheet X is, for example, an optical adhesive sheet disposed at a light passage location in a display panel. As a display panel, the display panel of personal devices, such as a mobile device and a wearable device, is mentioned, for example. The display panel has a laminated structure including elements such as, for example, a pixel panel, a polarizing film, a touch panel, and a cover glass. The adhesive sheet X is used to bond elements included in the laminated structure to each other in the manufacturing process of the display panel, for example.

The pressure-sensitive adhesive layer 10 is a pressure-sensitive adhesive layer formed from the above-described water-dispersible pressure-sensitive adhesive composition. The thickness of the pressure-sensitive adhesive layer 10 is preferably 50 μm or less, more preferably 40 μm or less, even more preferably 30 μm or less, and particularly preferably 20 μm or less, from the viewpoints of handleability and workability. The thickness of the pressure-sensitive adhesive layer 10 is preferably 3 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more, from the viewpoint of ensuring sufficient adhesiveness to the adherend.

The release liners L1 and L2 are elements for covering and protecting the pressure-sensitive adhesive sheet X (the pressure-sensitive adhesive layer 10), and are peeled off from the pressure-sensitive adhesive sheet X when the pressure-sensitive adhesive sheet X is used. The release liner L1 is, for example, a plastic film having flexibility. As the said plastic film, a polyethylene terephthalate film, a polyethylene film, a polypropylene film, and a polyester film are mentioned, for example. The thickness of the release liners L1 and L2 is, for example, 3 μm or more and, for example, 200 μm or less. The surfaces of the release liners L1 and L2 are preferably subjected to a release treatment.

The adhesive sheet (X) can be manufactured as follows, for example.

First, the water-dispersible pressure-sensitive adhesive composition described above is filtered through a filter (filtering step). Examples of the mesh size of the filter for filtration include 188 µm, 154 µm, 109 µm, 75 µm, 50 µm, 25 µm, 10 µm, 5 µm, 3 µm, 2 µm, and 1 µm.

Next, on the release liner L1, the above-mentioned water dispersion type pressure-sensitive adhesive composition is applied with a coater to form a coating film (coating film formation step). Examples of the application method include roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, and die coat. can In this process, a coater according to the coating method is used.

Next, the coating film on the release liner L1 is dried to form the pressure-sensitive adhesive layer 10 (drying step). The drying temperature is, for example, room temperature to 140°C. The drying time is, for example, 1 to 10 minutes.

Next, the release liner L2 is bonded to the exposed surface of the pressure-sensitive adhesive layer 10 on the release liner L1 as needed.

As described above, the pressure-sensitive adhesive sheet (X) can be produced from the water-dispersible pressure-sensitive adhesive composition.

As described above, the water-dispersible pressure-sensitive adhesive composition contains, in addition to the water-dispersible polymer and water, 0.1 to 1.5% by mass (ratio in solid content) of a carboxylic acid-based copolymer thickener and 1 to 3.7% by mass of a polyacrylic acid-based thickener. . Such a water-dispersible pressure-sensitive adhesive composition is suitable for ensuring the adhesive strength of the pressure-sensitive adhesive sheet (X) while achieving both low viscosity in the filtering step and moderate viscosity recovery in the coating step.

In the filtering process, the lower the viscosity of the water-dispersible pressure-sensitive adhesive composition, the easier it is to pass the water-dispersible pressure-sensitive adhesive composition through the filter, and the time required for the filtering process can be shortened.

During coating of the water-dispersible pressure-sensitive adhesive composition by the coater in the coating step, a relatively large shear force acts on the water-dispersible pressure-sensitive adhesive composition, and the viscosity of the composition temporarily decreases. After being applied on a plastic substrate (release liner), the water-dispersible pressure-sensitive adhesive composition is released from the shear force and its viscosity is restored. When the viscosity of the water-dispersible pressure-sensitive adhesive composition immediately after viscosity recovery is excessively low, the water-dispersible pressure-sensitive adhesive composition aggregates on the plastic substrate (occurrence of agglomeration).

When the viscosity immediately after viscosity recovery is excessively high, streaks are formed in the coating film of the water-dispersible pressure-sensitive adhesive composition (occurrence of streaks). However, since the water-dispersible pressure-sensitive adhesive composition described above has appropriate viscosity recovery after coating, the occurrence of clumps and streaks are suppressed.

[Example]

The present invention will be described concretely by showing examples below. However, the present invention is not limited to the examples. In addition, the specific numerical values such as the compounding amount (content), physical property values, and parameters described below are the compounding amounts (content), physical property values, parameters, etc. It can be replaced with an upper limit (a number defined as 'below' or 'less than') or a lower limit (a number defined as 'greater than' or 'greater than').

[Example 1]

<Preparation of water-dispersible polymer>

In a container, 30 parts by mass of ion-exchanged water, 85 parts by mass of 2-ethylhexyl acrylate, 13 parts by mass of methyl acrylate, 1.25 parts by mass of acrylic acid, 0.75 parts by mass of methacrylic acid, and t-lauryl as a chain transfer agent 0.035 parts by mass of mercaptan and 1.88 parts by mass of a reactive emulsifier (product name "Aquaron KH-1025", ammonium-α-sulfonate-ω-1-(allyloxymethyl)alkyloxypolyoxyethylene, manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) A mixture containing 0.02 parts by mass of a silane coupling agent (trade name "KBM-503", 3-methacryloxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.) was stirred with a homomixer to prepare a monomer emulsion.

On the other hand, a mixture containing 73 parts by mass of ion-exchanged water and 0.07 parts by mass of a reactive emulsifier (Aqualon KH-1025) was heated to 1 The mixture was stirred for an hour under a nitrogen atmosphere. Next, after adding 0.1 part by mass of 2,2'-azobis{2-[N-(2-carboxyethyl)amidino]propane} tetrahydrate as a polymerization initiator to this mixture, the above-described monomer emulsion was added to the mixture. It was added dropwise over 4 hours to advance the emulsion polymerization reaction. Next, the reaction solution was held at 60°C for 3 hours (aging). Next, after cooling the solution obtained in this way to room temperature, the pH of the solution was adjusted to 6.0 by adding 10% by mass ammonia aqueous solution. Next, 0.03 mass part of antiseptic|preservative (product name "Lebanax BX-150", the shoei chemical company make) was added to the said solution. As described above, an acrylic polymer emulsion containing a water-dispersible acrylic polymer as a water-dispersible polymer was prepared.

<Preparation of water-dispersible pressure-sensitive adhesive composition>

Regarding the acrylic polymer emulsion, per 100 parts by mass of the water-dispersible acrylic polymer, 1.00 parts by mass (product name "Aaron B-500", manufactured by Toagosei Co., Ltd.) of a carboxylic acid-based copolymer thickener (in terms of solid content) and a polyacrylic acid-based thickener (product name) "Aron A-10H", polyacrylic acid, weight average molecular weight 200,000, manufactured by Toagosei Co., Ltd.) 3.15 parts by mass (solid content conversion value), and a tackifier (product name "Tamanol E-200NT", terpene resin, Arakawa Chemical Industry manufacturer) 35 parts by mass (solid content conversion value) and leveling agent (product name "Neocol SW-C", dialkyl sulfosuccinate sodium, manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) 0.89 mass parts (solid content conversion value) were added and mixed. . Next, the mixture was adjusted to a solid content concentration of 25.5% by mass by adding ion-exchanged water, and then adjusted to pH 9.0 by adding 10% by mass ammonia aqueous solution. As described above, the water-dispersible pressure-sensitive adhesive composition (solid content concentration: 25.5% by mass) of Example 1 was produced (in Tables 1 and 2, the units of each numerical value representing the composition are 'parts by mass'). The prepared water-dispersible pressure-sensitive adhesive composition was filtered through a nylon mesh filter (product name 'N/Sha 4300KK', thickness: 110 μm, 80 mesh, mesh size: 188 μm, manufactured by Koyo Gosen Kogyo Co., Ltd.).

<Manufacture of adhesive sheet>

First, a water-dispersible pressure-sensitive adhesive composition was applied to the peeling-treated surface of a polyethylene terephthalate (PET) film (trade name 'Diafoil MRF38', manufactured by Mitsubishi Chemical Corporation) subjected to silicone peeling treatment to form a coating film. Next, the coating film on the PET film was dried in an oven for 3 minutes to form an adhesive layer having a thickness of 10 μm. Drying temperature was 100 degreeC. As described above, the PSA sheet of Example 1 (PET film-attached PSA sheet) was produced.

[Examples 2 to 8, Comparative Examples 1 to 10]

Examples 2 to 8 and Comparative Examples 1 to 10 in the same manner as in the water-dispersible pressure-sensitive adhesive composition of Example 1, except that the blending amounts of the carboxylic acid-based copolymer thickener and the polyacrylic acid thickener were changed as shown in Tables 1 and 2. Each water-dispersible pressure-sensitive adhesive composition was prepared. In Comparative Examples 1 and 3, no carboxylic acid-based copolymer thickener was used. In Comparative Examples 8 to 10, a polyacrylic acid thickener was not used.

Examples 1 to 8 and Comparative Examples 3 to 5, 7, Each PSA sheet of 9 (PET film-attached PSA sheet) was produced.

Adhesion of Comparative Examples 1, 2, 6, 8, and 10 in the same manner as in the production of the PSA sheet in Example 1, except that the blending amounts of the carboxylic acid-based copolymer thickener and the polyacrylic acid thickener were changed as shown in Table 2. The production work of the sheet was advanced. However, the water-dispersible pressure-sensitive adhesive composition applied on the PET film was clumped, and the pressure-sensitive adhesive sheets of Comparative Examples 1, 2, 6, 8, and 10 could not be produced.

<Viscosity measurement>

The viscosity of each water-dispersible pressure-sensitive adhesive composition of Examples 1 to 8 and Comparative Examples 1 to 10 was measured. Specifically, it is as follows.

First, the viscosity of the water-dispersible pressure-sensitive adhesive composition was measured using a rheometer viscometer (product name 'RheoStress1', manufactured by Hake) under conditions of a shear rate of 4s ^-1 and 30°C (first viscosity measurement). In this measurement, a cone-type rotor (cone No. 222-1267, cone diameter 35 mm, cone angle 0.5 degree) was used as a rotor for adding shear to the water-dispersible pressure-sensitive adhesive composition (the same is true for the second viscosity measurement described later). Tables 1 and 2 show the measured viscosity as the first viscosity η ₁ (Pa·s).

Subsequently, the shear rate was raised to 1×10 ⁴ s ^-1 , and shear was applied to the water-dispersible pressure-sensitive adhesive composition for 10 seconds under conditions of a shear rate of 1×10 ⁴ s ^-1 and 30°C. Subsequently, the shear rate was lowered to 4 s ^-1 , and 3 seconds after the shear rate was lowered, the viscosity of the water-dispersible pressure-sensitive adhesive composition was measured by a rheometer viscometer (RheoStress1) under the conditions of a shear rate of 4 s ^-1 and 30°C. (second viscosity measurement). Tables 1 and 2 show the measured viscosity as the second viscosity η ₂ (Pa·s). The ratio (η ₂ / ₁ ) of _the second viscosity η ₂ to the first viscosity η 1 is also shown in Tables 1 and 2.

<Filter Passability>

Filter passability of each water-dispersible pressure-sensitive adhesive composition of Examples 1 to 8 and Comparative Examples 1 to 10 was investigated. Specifically, 1 mL of water-dispersible pressure-sensitive adhesive composition was applied on a horizontally arranged nylon mesh filter (product name 'N/Sha 4300 KK', thickness 110 μm, 80 mesh, mesh size 188 μm, manufactured by Koyo Goshen Co., Ltd.) by a pipette. It was fed (placed) quietly and observed whether or not the composition passed through the filter under its own weight. Regarding the filter passability of the water-dispersible pressure-sensitive adhesive composition, the case where the water-dispersible pressure-sensitive adhesive composition passed the filter within 3 seconds by its own weight was evaluated as "good", and the case where it did not pass within 3 seconds was evaluated as "poor". . The results are shown in Tables 1 and 2.

<Wettability>

For each water-dispersible pressure-sensitive adhesive composition of Examples 1 to 8 and Comparative Examples 1 to 10, wettability to a plastic substrate was investigated. Specifically, it is as follows.

First, a water-dispersible pressure-sensitive adhesive composition was applied to the release-treated surface of a polyethylene terephthalate (PET) film (product name 'Diafoil MRF38', manufactured by Mitsubishi Chemical Co., Ltd.) subjected to silicone release treatment to form a coating film having a thickness of about 40 μm. Next, the coating film was visually observed. And, with respect to the difficulty of aggregation (suppression of aggregation) of the water-dispersible pressure-sensitive adhesive composition, the case where agglomeration did not occur in the coating film (water-dispersible pressure-sensitive adhesive composition) on the PET substrate was evaluated as "good", and the case where agglomeration occurred was evaluated as "poor". evaluated. In addition, with respect to the difficulty of forming stripes (suppression of stripes) in the water-dispersible pressure-sensitive adhesive composition, the case where no stripes were formed in the coating film on the PET substrate (water-dispersible pressure-sensitive adhesive composition) was evaluated as "good", and the case where stripes were formed was evaluated. It was evaluated as "poor". The evaluation results are shown in Tables 1 and 2. Difficulty in agglomeration and streak formation of the water-dispersible pressure-sensitive adhesive composition are indicators of wettability of the water-dispersible pressure-sensitive adhesive composition. For the water-dispersible pressure-sensitive adhesive compositions of Comparative Examples 1, 2, 6, 8, and 10, clumping occurred after coating on the PET film and a coating film could not be properly formed, so the appearance of stripes in the coating film could not be confirmed.

<Drop impact resistance test>

The adhesive strength of each of the PSA sheets of Examples 1 to 8 and Comparative Examples 3 to 5, 7, and 9 was examined by a drop impact resistance test. Specifically, it is as follows.

First, the PSA sheet with PET film was punched to obtain a rectangular frame-shaped PSA sheet piece with PET film (outer shape: 24.5 mm x 24.5 mm, width: 2 mm). Next, the PSA sheet pieces with PET film were bonded together along the four sides of the square first stainless plate (25 mm x 25 mm, thickness 3 mm). Next, the PET film was peeled from the pressure-sensitive adhesive sheet piece on the first stainless plate. Next, the first stainless plate and the square second stainless plate (50 mm x 50 mm, thickness 2 mm) having an opening (20 mm x 20 mm) in the center were placed through the adhesive sheet on the first stainless plate, and both plates While aligning the center position in a planar view in , it was compressed under conditions of a pressing force of 62 N and a pressing time of 10 seconds. In this way, a conjugate was obtained. Next, this conjugate was allowed to stand at 80°C for 30 minutes. Next, the bonded body was allowed to cool to 23°C.

Next, a cylindrical pedestal (height 50 mm, outer diameter 49 mm, inner diameter 43 mm) was installed on the stage of a DuPont impact tester (manufactured by Toyo Seiki Seisakusho), and then the bonded body described above was placed on this pedestal. Specifically, the second stainless plate in the assembly is disposed on the upper side, the lower surface of the second stainless plate is in contact with the upper end of the pedestal, and the first stainless plate on the lower side is disposed in the cylindrical cavity of the pedestal, The joined body was mounted on a pedestal (the first stainless plate is exposed upward through the opening of the second stainless plate). Next, a stainless steel cylindrical impact frame (bottom diameter: 6.2 mm) was placed on the first stainless plate facing the opening of the second stainless plate in the joint body.

Then, a drop impact test was conducted in which a weight was dropped in a vertical direction with respect to an impact frame on the bonded body by a DuPont impact tester. In the test for each bonded body, the mass (50g, 100g) and the drop height of the weight were changed so that the energy of impact acting on the bonded body through the impact frame sequentially increased, and between the first and second stainless plates of the assembled body. The weight was dropped several times until peeling occurred. When using a weight of 50 g in mass, the fall height of the weight was changed from 50 mm to 500 mm by 50 mm. Then, when using a weight of 100 g in mass, the fall height of the weight was changed by 50 mm from 300 mm to 500 mm. The cumulative value of the potential energy [load (kg) × gravitational acceleration 9.8 (m / s ² ) × height (m)] of the weight used until the separation between the first and second stainless plates of the assembly occurs, the drop impact energy ( J).

The average value of the drop impact energy resistance obtained by the three trials (n = 3) of the above drop impact resistance test is shown in Tables 1 and 2 as the drop impact energy resistance (J). In addition, with regard to the drop impact resistance of the adhesive sheet, a case where the drop impact energy was 0.4 J or more was evaluated as "good", and a case where the drop impact energy was less than 0.4 J was evaluated as "poor". The results are also shown in Tables 1 and 2.

[evaluation]

Each water-dispersible pressure-sensitive adhesive composition of Examples 1 to 8 contains, in addition to the water-dispersible polymer and water, 0.1 to 2.2 mass% (ratio in solid content) of a carboxylic acid-based copolymer thickener and 1.2 to 5.2 mass% of a polyacrylic acid-based thickener. . Such a water-dispersible pressure-sensitive adhesive composition exhibited good filter passability, suppressed clumps and streaks during application, and was able to form an adhesive sheet having good drop impact resistance.

In contrast, the water-dispersible pressure-sensitive adhesive composition of Comparative Example 1 (containing no carboxylic acid-based copolymer thickener and having a polyacrylic acid thickener ratio of 2.27% by mass) was unable to form a pressure-sensitive adhesive sheet due to clumping during coating. The water-dispersible pressure-sensitive adhesive composition of Comparative Example 2 (the ratio of the carboxylic acid-based copolymer thickener was 0.04% by mass and the ratio of the polyacrylic acid thickener was 2.26% by mass) was not able to form a pressure-sensitive adhesive sheet due to clumping during coating. The water-dispersible pressure-sensitive adhesive composition of Comparative Example 3 (containing no carboxylic acid-based copolymer thickener and having a polyacrylic acid thickener ratio of 4.23% by mass) could not form an adhesive sheet having good drop impact resistance. The water-dispersible pressure-sensitive adhesive composition of Comparative Example 4 (the ratio of the carboxylic acid copolymer thickener is 1.77% by mass and the ratio of the polyacrylic acid thickener is 2.23% by mass) has poor filter passability, and streaks are formed during coating. The water-dispersible pressure-sensitive adhesive composition of Comparative Example 5 (the ratio of the carboxylic acid-based copolymer thickener is 2.11% by mass and the ratio of the polyacrylic acid thickener is 2.22% by mass) has poor filter passability, streaks are formed during coating, and drop impact resistance is poor. A good PSA sheet could not be formed. The water-dispersible pressure-sensitive adhesive composition of Comparative Example 6 (a carboxylic acid-based copolymer thickener ratio of 0.73% by mass and a polyacrylic acid thickener ratio of 0.73% by mass) was unable to form a pressure-sensitive adhesive sheet due to clumping during coating. The water-dispersible pressure-sensitive adhesive composition of Comparative Example 7 (a carboxylic acid-based copolymer thickener ratio of 0.70 mass% and a polyacrylic acid thickener ratio of 3.86 mass%) could not form an adhesive sheet having good drop impact resistance. The water-dispersible pressure-sensitive adhesive composition of Comparative Example 8 (the ratio of the carboxylic acid-based copolymer thickener was 1.81% by mass and did not contain a polyacrylic acid thickener) was unable to form a pressure-sensitive adhesive sheet due to clumping during coating. The water-dispersible pressure-sensitive adhesive composition of Comparative Example 9 (the ratio of the carboxylic acid-based copolymer thickener is 2.86% by mass and does not contain a polyacrylic acid thickener) has poor filter passability, and an adhesive sheet having good drop impact resistance could not be formed. The water-dispersible pressure-sensitive adhesive composition of Comparative Example 10 (the ratio of the carboxylic acid-based copolymer thickener was 2.51% by mass and did not contain a polyacrylic acid thickener) was unable to form a pressure-sensitive adhesive sheet due to clumping during coating.

X: adhesive sheet
10: adhesive layer
L1, L2: release liner

Claims (8)

A water-dispersible pressure-sensitive adhesive composition containing a water-dispersible polymer, a carboxylic acid-based copolymer thickener, a polyacrylic acid thickener, and water,
The ratio of the carboxylic acid-based copolymer thickener in the solid content of the water-dispersible pressure-sensitive adhesive composition is 0.1% by mass or more and 1.5% by mass or less,
A water-dispersible pressure-sensitive adhesive composition wherein the ratio of the polyacrylic acid thickener in the solid content is 1% by mass or more and 3.7% by mass or less. According to claim 1,
The water-dispersible pressure-sensitive adhesive composition, wherein the total ratio of the carboxylic acid-based copolymer thickener and the polyacrylic acid thickener in the solid content is 2% by mass or more and 4.2% by mass or less. According to claim 1,
A water-dispersible pressure-sensitive adhesive composition having a shear rate of 4 s ^-1 and a viscosity of 0.8 Pa·s or less under conditions of 30°C. According to claim 1,
A water-dispersible pressure-sensitive adhesive composition having a viscosity of 0.9 Pa·s or more and 1.5 Pa·s or less after shearing under conditions of a shear rate of 1×10 ⁴ s ^-1 and 30°C and a shear rate of 4 s ^-1 and 30°C. According to claim 1,
The water-dispersible pressure-sensitive adhesive composition further contains a tackifier. According to claim 1,
The water-dispersible pressure-sensitive adhesive composition further contains a leveling agent, the water-dispersible pressure-sensitive adhesive composition. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 6. According to claim 7,
The pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer has a thickness of 40 μm or less.

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